Method for operating and/or monitoring an HVAC system

ABSTRACT

A method for operating and/or monitoring an HVAC system (10), in which a medium circulating in a primary circuit (26) flows through at least one energy consumer (11, 12, 13), the medium entering with a volume flow (φ) through a supply line (14) into the energy consumer (11, 12, 13) at a supply temperature (Tv) and leaving the energy consumer (11, 12, 13) at a return temperature (TR) via a return line (15), and transferring heat or cooling energy to the energy consumer (11, 12, 13) in an energy flow (E). A control unit (21) adaptively operates the system by empirically determining the dependence of the energy flow (F) and/or the temperature difference ΔT between supply temperature (Tv) and return temperature (TR) on the volume flow (φ) for the energy consumers (11, 12, 13) in a first step, and by operating and/or monitoring the HVAC system (10) according to the determined dependency or dependencies in a second step.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a Continuation of application Ser. No. 14/232,759 filed Mar. 5,2014, claiming priority based on International Application No.PCT/EP2012/064557 filed Jul. 25, 2012, claiming priority based onSwitzerland Patent Application No. 01458/11, filed Sep. 5, 2011, thecontents of all of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to the field of in-door climatetechnology. Said present invention relates to a method for operatingand/or monitoring an HVAC system in accordance with the preamble ofpatent claim 1 as well as an HVAC system for carrying out the method.The term HVAC is an acronym that is used in English-speaking countriesfor heating, ventilation and air conditioning, which usually denotes thefield of application of in-door climate technology.

STATE OF THE ART

HVAC systems are often used in larger buildings or building complexes.In this case a central energy-generating system provides in acirculating manner the heat and/or cold energy by means of an energycarrier medium in a primary circuit. Then in the individual buildings orparts of buildings this heat and/or cold energy is and/or are extractedin a controlled way, usually by means of a local heat exchanger, andtransferred to a secondary circuit, where it is used for purposes ofin-door climate management to heat and/or cool the individual rooms orthe like. The diagram of such a system is shown in FIG. 3, for example,of the publication U.S. Pat. No. 5,347,825.

The flow of energy E delivered to the respective secondary circuit(energy per unit of time or power) is obtained in accordance with theequation E=k·φ·ΔT, where k is a constant, containing the specificenergy; φ denotes the volumetric flow rate of the energy carrier mediumon the primary side of the heat exchanger; and ΔT gives the temperaturedifferential between the supply temperature T_(v) and the returntemperature T_(R) on the primary side of the heat exchanger. Thetemperature differential ΔT usually shows a dependence on the volumetricflow rate φ and decreases significantly as the volumetric flow rateincreases.

In the closed loop control process of the extraction process at therespective heat exchanger, the cold or heat energy requirement in theassociated secondary circuit has to be taken into consideration, on theone hand. Yet, on the other hand, efficiency considerations figureprominently. That is, the goal is to avoid operating conditions, atwhich the medium is circulated in the primary circuit with a largepumping capacity, while at the respective heat exchangers only acomparatively small amount of energy is extracted at small temperaturedifferentials ΔT, because the flow of energy E does not increaselinearly with the volumetric flow rate φ, but rather flattens off moreand more as the volumetric rate of flow increases.

DE 34 25 379 A1 describes a method for controlling a heat transferstation, in which heat is passed from a primary loop by way of a heatexchanger to a secondary loop. In order to control the supplytemperature in the secondary loop, a weather-dependent setpoint valuefor the return temperature in the primary loop is determined while atthe same time taking into consideration a maximum temperature, and isused to adjust the primary flow of heat flowing through the heatexchanger. As the reference variable for setting the setpoint value ofthe primary return temperature, the temperature of the primary supplyflow is measured and fed, together with the measured temperature valuein the primary return flow, to a control unit for adjusting the heatflow in the primary loop in conjunction with a measurement of the flowrate. In this case the closed loop control of the heat flow in theprimary loop is carried out taking into consideration a limited maximumreturn temperature (the principle of return temperature limit).

The publication EP 0 035 085 A1 discloses a system for transporting heatby means of a fluid having at least one heat source, which is connectedby lines to at least one heat consumer; a valve; which is interposed inthe lines and which is provided for adjusting the heat that is to betransported; two temperature sensors, of which one is interposed in aline that conducts the fluid to the heat consumer and one is interposedin a line that conducts the fluid away from the heat consumer; aflowmeter, which is interposed in one of these lines; and a device,which is connected to the temperature sensors and the flowmeter andcomprises means for determining the transported heat from the measuredtemperatures and flow rates. The special feature lies in the fact thatthe device is connected to the valve and comprises means to control thevalve in such a way that the flow of heat from the heat source to theheat consumer is interrupted, when the flow rate, which is measured bythe flowmeter, drops to a lower limit value. The purpose of thisarrangement is to avoid too large an error in finding the quantity ofheat consumed. An empirical determination of the dependence of the flowof energy and the temperature differential on the volumetric rate offlow is not disclosed.

This document DE 2 216 464 A1 describes an open and closed loop controlunit for optimal detection of the quantities of heat by means of heatmeters or heat quantity meters according to the flow principle. The flowrate and the temperature differential between the supply and the returnare always controlled in such a way that the heat metering device worksin its optimal range in terms of the measurement technique and wear inboth the flow rate range and the temperature differential range.

Although the document shows in FIG. 1 (c) a graph that shows thedependence of the temperature differential on the flow, the respectivedescription (page 10, lines 4 to 7) reads explicitly that thespecification of the diagram is based on the assumption that the k valueof the heating element is independent of the temperature and thetemperature differential.

This statement makes it clear that it is not an empirically determinedgraph.

The publication U.S. Pat. No. 6,352,106 B1 describes a self-balancingmodulating control valve for use in HVAC systems with a variablevolumetric rate of flow for supplying multiple energy consumers. Whenthis control valve is used in the respective energy consumer, it helpsto reduce the maximum pumping power in the primary loop under alloperating conditions. The valve requires only a very small pressuredifferential and yet works effectively under any and all consumption andflow conditions. An essential part is the specification of a limit valuefor a temperature or more specifically a temperature differentialmeasured at the consumer. When this temperature or more specificallytemperature differential is reached, the control range of the valve isre-established.

The publication WO 98/25086 A1 discloses a control unit for an HVACsystem having a valve that reacts to an input from a sensor, in order torestrict or permit the flow of a fluid through the valve as a functionof the conditions in the measurement environment. Furthermore, a valvecontrol unit and a flowmeter are provided. The flowmeter is disposed inthe valve body, and the valve control unit is programmed with a maximumamount of flow through the valve. The rate of flow through the valve islimited by the valve control unit to the programmed maximum value.

Finally the publication DE 35 33 160 A1 discloses a control arrangementfor a central consumer unit that is connected to a district heatingsystem. Attached to the central consumer unit are a measuring device,consisting of a flow measuring device, which measures the flow of thedistrict heating water through the central consumer unit; temperaturesensors for measuring the supply temperature and the return temperatureof the district heating water; and an integrating device for calculatingand integrating the consumed thermal energy by means of the measuredflow values and the temperature values; as well as a variable,flow-regulating valve for regulating the flow of the district heatingwater through the central consumer unit. Furthermore there is a flowand/or energy limiting unit, which has a sampling member, which isconnected to the flow measuring device and/or the integrating device, inorder to sample the flow of the district heating water through thecentral consumer unit and/or the energy extracted from the districtheating system; a reference member, which compares the value of the flowand/or the energy extracted with a maximum value that is predeterminedfor this purpose; and a control member, which is connected to theflow-regulating valve and which reduces the flow and/or the energy tosaid maximum value by reducing the flow through the flow-regulatingvalve, when the flow and/or the energy extracted exceeds thepredetermined maximum value mentioned, because, for example, the heatgenerating system of the district heating system does not cover theenergy demand of all of the consumers connected to the district heatingsystem.

All of these solutions known from the prior art have in common that thelimit values that are used must be determined without knowing thespecial features of the respective energy consumer or more specificallythe secondary loop. Another drawback is that the system modifications,which should affect the set limit values, are not recognized and, thus,cannot be taken into consideration.

BRIEF SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide a methodthat conforms to its genre and avoids the disadvantages of the knownmethods. In particular, the method according to the invention ischaracterized by the fact that the control process adjusts itself in anadaptive fashion to the actual properties of the respective energyconsumer and can also recognize and consider these properties, evenafter changes, in particular a degradation, occurring after a prolongedperiod of operation.

Furthermore, the object of the invention is to provide an HVAC systemfor carrying out the method according to the invention.

The aforementioned and other engineering objects are achieved by meansof the features disclosed in claims 1 and 12.

In the inventive method for operating and/or monitoring an HVAC system amedium, which circulates in a primary circuit, flows through at leastone energy consumer, said medium entering at a volumetric flow rate intoan energy consumer through a supply line at a supply temperature andleaving the energy consumer at a return temperature by way of a returnline and, in so doing, releases heat energy or cold energy to the energyconsumer in a flow of energy. The method is characterized by the factthat the dependence of the flow of energy and/or the temperaturedifferential ΔT between the supply temperature and the returntemperature on the volumetric flow rate is determined empirically forthe respective energy consumer in a first step and that the HVAC systemis changed and/or operated in accordance with the determined dependenceand/or dependences in a second step. The medium circulating in theprimary circuit may be, in particular, water. The energy consumer cantransfer the extracted energy to, for example, air or water, in order tocool or heat particular rooms.

A change in the HVAC system may be necessary, when the empiricallydetermined data show that the system is not properly sized or deviatessignificantly from the specified properties. As a result, it may benecessary, for example, to replace the heat exchanger that is being usedwith a heat xchanger of a different size or to make other changes to thesystem. A change in operation could consist of changing certainpredetermined limit values for the volumetric rate of flow, the flow ofenergy or temperatures that are important for the control process.

One embodiment of the method according to the invention is characterizedby the fact that in order to determine empirically the dependence of theflow of energy and/or the temperature differential ΔT between the supplytemperature and the return temperature on the volumetric rate of flow,while the system is running, over a sufficiently long period to time,the volumetric flow rate and the temperature differential ΔT between thesupply temperature and the return temperature are measuredsimultaneously at different points in time and, if desired, theassociated flow of energy is determined for each of these points in timefrom the associated measurement values and assigned to the respectivevolumetric rate of flow. Then the various measurement points yield agraph with a point distribution that resembles a curve and from whichthe various control engineering and system engineering conclusions canbe drawn.

An additional embodiment of the method according to the invention ischaracterized by the fact that the dependence of the flow of energy onthe volumetric flow rate is determined empirically, and that on thebasis of the determined dependence, an upper limit value of the flow ofenergy is established, and this upper limit value is not exceeded whilethe HVAC system is running. This arrangement offers advantages similarto those described in DE 35 33 160 A1, which is cited in theintroduction, with the difference that the limit value can be adjustedin an adaptive manner to the respective consumer, and that the entiresystem can be operated under optimal conditions not only when the systemis newly installed, but also after the system has been operating for alonger period of time.

In an alternative embodiment the dependence of the temperaturedifferential ΔT between the supply temperature and the returntemperature on the volumetric flow rate is determined empirically, andon the basis of the determined dependence, a lower limit value of thetemperature differential ΔT between the supply temperature and thereturn temperature is established, and this lower limit value is notundershot while the HVAC system is running.

Another embodiment of the method according to the invention ischaracterized by the fact that the dependence of the flow of energyand/or the temperature differential ΔT between the supply temperatureand the return temperature on the volumetric flow rate is determinedempirically at the start of the operation in a newly installed HVACsystem and that the continued operation takes place in accordance withthe determined dependence or rather dependences.

An additional embodiment of the method according to the invention ischaracterized by the fact that the dependence of the flow of energyand/or the temperature differential ΔT between the supply temperatureand the return temperature on the volumetric rate of flow is determinedempirically at the start of the operation in a newly installed HVACsystem and that the HVAC system or more specifically the individualcomponents are changed or replaced, when the empirically determineddependences make it necessary.

According to another embodiment, the dependence of the flow of energyand/or the temperature differential ΔT between the supply temperatureand the return temperature on the volumetric flow rate is repeatedlydetermined empirically at longer time intervals, and the results thatare obtained in each case are compared with each other, in order todetermine by means of the comparison a degradation of the system infunction or effect.

Based on the aforesaid, it may be necessary that the measurement valuesare scaled, in particular, by means of a mathematical model of theenergy consumer for purposes of comparison, or that other comparablemeasurements are used for comparison, when important operatingparameters, such as the supply temperature, have changed significantlyin the meantime.

Another embodiment of the method according to the invention ischaracterized by the fact that first means for determining thetemperature differential ΔT between the supply temperature and thereturn temperature as well as second means for determining thevolumetric rate of flow are provided in the HVAC system to carry out theoperation, and that the first and second means are used for empiricallydetermining the dependence of the flow of energy and/or the temperaturedifferential ΔT between the supply temperature and the returntemperature on the volumetric rate of flow. This arrangement makes itpossible to use already existing measuring devices and to dispense withthe installation of additional special test equipment.

Preferably the empirical determination of the dependence of the flow ofenergy and/or the temperature differential ΔT between the supplytemperature and the return temperature on the volumetric rate of flow iscarried out while the HVAC system is running. In this way the system canbe monitored without disturbing the ongoing operations.

Furthermore, it is advantageous, if a control valve is used for openand/or closed loop control of the volumetric rate of flow in the primarycircuit, and the pressure differential, occurring at the control valve,is determined from the measured volumetric flow rate in accordance withthe characteristic curves of the control valve and the valve position,and, if required, is used for controlling and/or monitoring purposes.

The inventive HVAC system for carrying out the method comprises aprimary circuit, which is traversed by the flow of an energytransporting medium, and at least one energy consumer, which isconnected to the primary circuit by way of a supply line and a returnline. In this case first means for determining the temperaturedifferential ΔT between the supply temperature and the returntemperature at the energy consumer as well as second means fordetermining the volumetric rate of flow through the energy consumer areprovided. Said inventive HVAC system is characterized by the fact thatthird means are connected to the first and second means, and said thirdmeans receive and store the measurement values, which are outputtedsimultaneously by the first and second means, at different times.

Preferably the third means comprise a data logger that receives themeasurement values, which are assigned to each other, and stores saidcomplementary values for subsequent use.

In this respect the third means are configured for calculating andassigning the flow of energy from and/or to the measurement values thatare outputted by the first and second means.

One embodiment of the HVAC system according to the invention ischaracterized by the fact that the HVAC system includes a control unit,which controls and/or regulates by way of a control valve the volumetricrate of flow through the energy consumer and into which limit values forthe flow of energy and/or the temperature differential ΔT between thesupply temperature and the return temperature can be entered.

Preferably the control unit is connected to the first and second means.

An additional embodiment of the HVAC system is characterized by the factthat the first means comprise a first temperature sensor for measuringthe supply temperature and a second temperature sensor for measuring thereturn temperature, and that the second means comprise a flowmeter thatis disposed in the supply line or the return line of the energyconsumer.

According to another embodiment of the HVAC system, the energy consumercomprises a heat exchanger, by means of which energy is released to asecondary loop.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention shall be explained in detail below with reference to someexemplary embodiments in conjunction with the drawings. The drawingsshow in:

FIG. 1 a section of a simplified schematic of an HVAC system accordingto one exemplary embodiment of the invention.

FIG. 2 the profiles of the volumetric rate of flow φ and the temperaturedifferential ΔT between the supply temperature and the returntemperature in a real HVAC system, where said profiles were measuredover a period of about one day.

FIG. 3 the pairs of values E_(i)(φ_(i)) and ΔT_(i)(φ_(i)), which aredetermined from the profiles in FIG. 2 according to the invention andwhich yield in each case a characteristic curve.

FIG. 4 a characteristic curve E(φ), which is abstracted from the drawingin FIG. 3, with the plotted limit value E_(max); and

FIG. 5 a schematic representation of a change in the curve E (φ) caused,for example, by a degradation of the system over a prolonged period ofoperation.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a section of a simplified schematic of an HVAC systemaccording to one exemplary embodiment of the invention. The HVAC system10 in FIG. 1 comprises at least one energy consumer in the form of awater/air heat exchanger 11, which is traversed by the flow of air onthe secondary side. Then this air is conducted to an air duct 12 by afan or blower 13. On the primary side the heat exchanger or morespecifically the heat transfer device 11 is connected to a primarycircuit 26 by means of a supply line 14 and a return line 15. An energytransporting medium, in particular water, feeds heat or cold energy tothe heat exchanger 11 from a central heat or cold source, which is notdepicted in the drawing, by means of said primary circuit. The mediumenters the heat exchanger 11 at a supply temperature T_(v) by way of thesupply line 14 and issues again from the heat exchanger 11 at a returntemperature T_(R) by way of the return line 15.

In order to determine the flow rate of the medium flowing through theheat exchanger 11, a flowmeter 18 of the customary design is disposed inthe supply line 14. It goes without saying that the flowmeter may alsobe arranged, as an alternative, in the return line 15. In order toregulate or control the flow rate, a control valve 19 of the typicaldesign is disposed in the return line 15; and this control valve can beadjusted by means of a controllable drive 20.

In order to measure the supply temperature T_(V), a temperature sensor16 is provided in the supply line. However, the supply temperature T_(v)can also be measured at any point in the primary circuit, since thistemperature is usually the same for the primary loop in its entirety andfor all of the energy consumers. The return temperature T_(R) ismeasured by means of an additional temperature sensor 17, which isarranged on the return line 15.

During normal operation the medium enters the heat exchanger 11 at thesupply temperature T_(V) by way of the supply line. In said heatexchanger the medium releases the heat or cold energy to the air flowingthrough the air chamber 12 and then leaves again at a return temperatureT_(R) that deviates from the supply temperature T_(V). The flow ofenergy E that is transferred to the air flow on the secondary side isobtained, according to the aforementioned formula, from the volumetricrate of flow φ on the primary side and the temperature differential ΔTbetween the supply temperature T_(V) and the return temperature T_(R).Of interest is only the amount of the flow of energy, against theequation of the absolute value of the temperature differential ΔT.

In order to control the transfer of energy to the energy consumer, thereis a control unit 21, to which the measurement values from thetemperature sensors 16 and 17 and the flowmeter 18 are fed. Then thecontrol unit 21 controls the control valve 19 in accordance with theclosed loop control characteristics by way of the drive 20. FIG. 2 showsthe profiles of the volumetric rate of flow φ and the temperaturedifferential ΔT between the supply temperature and the returntemperature in a real HVAC system during the cooling operation, wheresaid profiles were measured as a function of the time over a period ofabout one day. FIG. 2 shows very clearly the nocturnal decrease betweenmidnight (about 12:00:00 o'clock) and the early morning (about 7:00:00o'clock), where the volumetric rate of flow φ practically disappears andthe temperature differential ΔT is very low, and the high valuesstarting after noon (about 13:00:00 o'clock).

If in such an operation with a varying volumetric rate of flow φ and achanging temperature differential ΔT at many different points in timet_(i), the associated pairs of values φ_(i) and ΔT_(i) are logged andplotted on a graph ΔT_(i) (φ_(i)), the result is a point distribution,as shown for the diamond-shaped points in FIG. 3. In FIG. 3 thevolumetric rate of flow is given in gallons per minute (GPM; 1 GPM isequivalent to 3.785 l/min); the temperature differential is given indegrees Fahrenheit (° F.).

Then the associated flow of energy E_(i) can be calculated from thepairs of values φ_(i) and ΔT_(i). The corresponding point distributionE_(i) (φ_(i)) with the square points is also plotted on the graph inFIG. 3.

The results of the two point distributions ΔT_(i)(φ_(i)) andE_(i)(φ_(i)) are the characteristic curves for the energy consumer (heatexchanger 11 plus the secondary circuit); and these characteristiccurves can be evaluated for the operation of the system and theevaluation and monitoring of the system. Such a characteristic E (φ)curve with the curve profile V1 is shown in FIG. 4 as a single dottedline.

This single dotted line shows again the point distribution E_(i)(φ_(i))from FIG. 3. Based on the curve, it is now possible to select andspecify in an adaptive manner a maximum energy flow value E_(max) thatis optimally adapted to the respective energy consumer, and that shouldnot be exceeded during closed loop control of the energy consumerassociated with this curve. Such a maximum energy flow value E_(max) isobtained, according to FIG. 3, for example, from the location (upperdotted circle in FIG. 3), at which the point distribution E_(i)(φ_(i))reaches a region B, which can be referred to as the “zone of energywaste.” The lower dotted circle in FIG. 3 marks the corresponding entryof the point distribution ΔT_(i) (φ_(i)) into this zone (here, too, acurve comparable to the one in FIG. 4 can be created), so that a minimumtemperature differential ΔT_(min) can also be used as the limit value.

In the present case the sensors 16 to 18, which are present in any eventfor the closed loop control process, are used for determining thecharacteristic point distributions or more specifically thecharacteristic curves ΔT_(i) (φ_(i)) and E_(i)(φ_(i)). However, it isalso conceivable within the scope of the invention to provideindependent sensors for this determination, so that this determinationcan be carried out independently of the rest of the open and/or closedloop control process.

In the example from FIG. 1, in which there are no independent sensors, adata logger 22 is formed inside the control unit 21. This data loggercan be implemented through special programming of a microprocessor,which is used in the control unit 21. However, said data logger can alsobe present as an independent electronic unit. The data logger 22 logsthe measurement points φ_(i) and ΔT_(i) in pairs at defined points intime t_(i) and saves them in a memory unit. Added to this is then thecorresponding calculated energy flow value E_(i). Then the resultingpoint distributions ΔT_(i)(φ_(i)) and E_(i)(φ_(i)) can be displayed, forexample, on an output unit 24 and, as a result, are available to thesystem operator as information about the respective status and thecharacteristic properties of the system. Based on the outputtedinformation, suitable limit values can be entered into the control unit21 by means of an input unit 23. However, it is, of course, alsopossible to let the adaptive specification of the limit values runautomatically according to a given algorithm in the control unit 21itself.

In addition to the adaptive specification of the limit values ΔT_(min)and/or E_(max), the empirical determination of the characteristicdistribution of the measurement points or more specifically thecharacteristic curves can be used to monitor the system. In the eventthat the transfer properties of the heat exchanger 11 degrade, forexample, over a longer period of operation (for example, due tocalcification, rusting or the like), the flow of energy E decreaseswhile the volumetric rate of flow φ remains constant. If then at a muchlater time (for example, months or years) a measurement/determination ofthe point distribution E_(i) (φ_(i)) is and/or are repeated, the resultfor the resulting curve profiles is the picture shown in FIG. 5. Thecurve determined at a later time has a curve profile V2, which deviatessignificantly from the original curve profile V1, because for aparticular value φ1 of the volumetric flow rate the result is a flow ofenergy E that is reduced by ΔE. Such a change implies a degradation ofthe system that can then be corrected in a targeted way within theframework of maintenance/repair work. For continuous monitoring, routinedetermination of the characteristic point distributions is practical.

However, a direct comparison of two such curve profiles V1 and V2 isonly possible if the other important operating parameters, such as thesupply temperature T_(v) and the (air) flow rate in the secondary loopof the heat exchanger 11, do not change in the meantime or change onlynegligibly. If, however, these variables change significantly, themeasured values have to be scaled accordingly for comparison purposeseither, in particular, by means of a mathematical model of the heatexchanger 11, or other (comparable) measurement results, which have beenobtained with similar operating parameters, have to be used forcomparison purposes.

The measurement of the volumetric rate of flow φ by means of theflowmeter 18 can also be used advantageously to determine the pressuredrop (pressure differential Δp between the valve inlet and the valveoutlet) that occurs at the control valve 19 and to make said pressuredrop useful for controlling and/or monitoring the system. The net resultis a “virtual pressure sensor,” which makes directly acting pressuremeasuring means superfluous. For evaluation purposes, the correlationbetween the volumetric rate of flow φ and the pressure differential Δpis used, and said correlation can be described with the equation for thevalve characteristic φ=K_(v) √Δp, where K_(v) denotes the flowcoefficient that depends on the valve position (valve lift), in that fora known family of characteristics for the control valve 19, for whichsaid family of characteristics is stored in the control unit 21, theposition of the control valve 19 together with the measured volumetricflow rate φ is transmitted to the control unit 21, where thecorresponding pressure differential Δp can be determined, and/or if onepressure value is known, the other pressure value of the pressuredifferential can be determined and subsequently used. It is obvious thatsuch a “virtual pressure sensor” can also be implemented with othervalves and in other contexts.

The proposed empirical determination of the characteristic curves and/orproperties of the system offers the following advantages:

-   -   If a significant sub-functioning of the heat exchanger is        determined, a safety circuit can be provided.    -   Specific limit values for ΔT and/or E lead to savings in the        energy consumption of the pumps and a reduction in the cooling        capacity in the central station.    -   The recommissioning of the system is facilitated.    -   The efficiency of the heat exchanger can be easily checked.    -   The system can be continuously adapted and improved.    -   The developments and improvements of the system can be        documented.    -   The function of the heat exchanger can be compared with the        manufacturer's data.    -   A problem can be quickly identified and corrected with the        acquired data. A necessary replacement of the heat exchanger can        also be derived from the data.    -   Easy diagnosis is possible for:        -   a. fluid flow in the wrong direction        -   b. non-functioning sensors        -   c. obstruction of flow        -   d. low ΔT

LIST OF REFERENCE NUMERALS

10 HVAC system

11 heat exchanger (heat transferring device)

12 air duct

13 fan

14 supply line

15 return line

16 temperature sensor (supply temperature)

17 temperature sensor (return temperature)

18 flowmeter

19 control valve

20 drive

21 control unit

22 data logger

23 input unit

24 output unit

25 memory unit

26 primary circuit

27 secondary circuit

E flow of energy

ΔT temperature differential

φ volumetric rate of flow

V1, V2 curve profile

The invention claimed is:
 1. A method for adaptively operating and/ormonitoring a Heating, Ventilation and Air Conditioning (HVAC) system(10) under control of a controller (21, 22), the method comprising:circulating a medium in a primary circuit (26), such that the mediumflows through at least one energy consumer (11, 12, 13), the mediumentering at a volumetric rate of flow (φ) into an energy consumer (11,12, 13) through a supply line (14) at a supply temperature (T_(V)) andleaving the energy consumer (11, 12, 13) at a return temperature (T_(R))by way of a return line (15) and, in so doing, releases heat energy orcold energy to the energy consumer (11, 12, 13) in a flow of energy (E),empirically determining a dependence of the flow of energy (E) and/or atemperature differential ΔT between the supply temperature (T_(V)) andthe return temperature (T_(R)) on the volumetric flow rate (φ) for therespective energy consumer (11, 12, 13), adaptively changing operationof the HVAC system (10) in accordance with the determined dependenceand/or dependences, wherein the dependence of the flow of energy (E) onthe volumetric flow rate (φ) is repeatedly determined empirically atvarying time intervals by the controller, whereby the volumetric flowrate (φ) and the temperature differential ΔT between the supplytemperature (T_(V)) and the return temperature (T_(R)) are measuredsimultaneously at different points in time and, if desired, theassociated flow of energy (E) is determined for each of the points intime from associated measurement values and assigned to a respectivevolumetric rate of flow (φ) in order to determine empirically thedependence of the flow of energy (E) on the volumetric flow rate (φ),while the system is running, over a sufficiently long period of time,and wherein, on the basis of the determined dependence, an upper limitvalue (E_(max)) of the flow of energy (E) is established, and said upperlimit value is not exceeded while the HVAC system (10) is running. 2.The method, as claimed in claim 1, wherein the dependence of the flow ofenergy (E) on the volumetric flow rate (φ) is determined empirically ata start of the operation in a newly installed HVAC system (10), and theHVAC system (10) or more specifically the individual components arechanged or replaced, when the empirically determined dependences make itnecessary.
 3. The method, as claimed in claim 1, wherein temperaturesensors (16, 17) for determining the temperature differential ΔT betweenthe supply temperature (T_(V)) and the return temperature (T_(R)) aswell as the at least one flow sensor (18) for determining the volumetricflow rate (φ) are provided in the HVAC system (10) for carrying out theoperation, and wherein the temperature and flow sensors (16, 17 and/or18) are used for empirically determining the dependence of the flow ofenergy (E) on the volumetric flow rate (φ).
 4. A method for adaptivelyoperating and/or monitoring a Heating, Ventilation and Air Conditioning(HVAC) system (10) under control of a controller (21, 22), the methodcomprising: circulating a medium in a primary circuit (26), such thatthe medium flows through at least one energy consumer (11, 12, 13), themedium entering at a volumetric rate of flow (φ) into an energy consumer(11, 12, 13) through a supply line (14) at a supply temperature (T_(V))and leaving the energy consumer (11, 12, 13) at a return temperature(T_(R)) by way of a return line (15) and, in so doing, releases heatenergy or cold energy to the energy consumer (11, 12, 13) in a flow ofenergy (E), empirically determining a dependence of a temperaturedifferential ΔT between the supply temperature (T_(V)) and the returntemperature (T_(R)) on the volumetric flow rate (φ) for the respectiveenergy consumer (11, 12, 13), adaptively changing operation of the HVACsystem (10) in accordance with the determined dependence and/ordependences, wherein the dependence of the temperature differential ΔTbetween the supply temperature (T_(V)) and the return temperature(T_(R)) on the volumetric flow rate (φ) is repeatedly determinedempirically at varying time intervals by the controller, whereby thevolumetric flow rate (φ) and the temperature differential ΔT between thesupply temperature (T_(V)) and the return temperature (T_(R)) aremeasured simultaneously at different points in time and, if desired, theassociated flow of energy (E) is determined for each of the points intime from associated measurement values and assigned to a respectivevolumetric rate of flow (φ) in order to determine empirically thedependence of the temperature differential ΔT between the supplytemperature (T_(V)) and the return temperature (T_(R)) on the volumetricflow rate (φ), while the system is running, over a sufficiently longperiod to time, wherein, on the basis of the determined dependence, alower limit value (ΔT_(min)) of the temperature differential ΔT betweenthe supply temperature (T_(V)) and the return temperature (T_(R)) isestablished.
 5. The method, as claimed in claim 4, wherein thedependence of the temperature differential ΔT between the supplytemperature (T_(V)) and the return temperature (T_(R)) on the volumetricflow rate (φ) is determined empirically at a start of the operation in anewly installed HVAC system (10), and the HVAC system (10) or morespecifically the individual components are changed or replaced, when theempirically determined dependences make it necessary.
 6. The method, asclaimed in claim 4, wherein temperature sensors (16, 17) for determiningthe temperature differential ΔT between the supply temperature (T_(V))and the return temperature (T_(R)) as well as at least one flow sensor(18) for determining the volumetric flow rate (φ) are provided in theHVAC system (10) for carrying out the operation, and wherein thetemperature and flow sensors (16, 17 and/or 18) are used for empiricallydetermining the dependence of the temperature differential ΔT betweenthe supply temperature (T_(V)) and the return temperature (T_(R)) on thevolumetric flow rate (φ).
 7. A method for adaptively operating and/ormonitoring a Heating, Ventilation and Air Conditioning (HVAC) system(10) under control of a controller (21, 22), the method comprising:circulating a medium in a primary circuit (26), such that the mediumflows through at least one energy consumer (11, 12, 13), the mediumentering at a volumetric rate of flow (φ) into an energy consumer (11,12, 13) through a supply line (14) at a supply temperature (T_(v)) andleaving the energy consumer (11, 12, 13) at a return temperature (T_(R))by way of a return line (15) and, in so doing, releases heat energy orcold energy to the energy consumer (11, 12, 13) in a flow of energy (E),empirically determining a dependence of the flow of energy (E) and/or atemperature differential ΔT between the supply temperature (T_(V)) andthe return temperature (T_(R)) on the volumetric flow rate (φ) for therespective energy consumer (11, 12, 13), adaptively changing operationof the HVAC system (10) in accordance with the determined dependenceand/or dependences, wherein the dependence of the flow of energy (E)and/or the temperature differential ΔT between the supply temperature(T_(V)) and the return temperature (T_(R)) on the volumetric flow rate(φ) is repeatedly determined empirically at varying time intervals bythe controller, whereby the volumetric flow rate (φ) and the temperaturedifferential ΔT between the supply temperature (T_(V)) and the returntemperature (T_(R)) are measured simultaneously at different points intime and, if desired, the associated flow of energy (E) is determinedfor each of these points in time from associated measurement values andassigned to a respective volumetric rate of flow (φ) in order todetermine empirically the dependence of the flow of energy (E) and/ortemperature differential ΔT between the supply temperature (T_(V)) andthe return temperature (T_(R)) on the volumetric flow rate (φ), whilethe system is running, over a sufficiently long period to time, whereinresults that are obtained in each case are compared with each other bythe controller, in order to determine by the comparison a degradation ofthe system in function or effect, and wherein the measurement values arescaled, in particular, by means of a mathematical model of the energyconsumer (11, 12, 13) for purposes of comparison, or wherein othercomparable measurements are used for comparison, when specifiedoperating parameters have changed significantly in the meantime.
 8. Themethod, as claimed in claim 7, wherein the dependence of the flow ofenergy (E) and/or the temperature differential ΔT between the supplytemperature (T_(V)) and the return temperature (T_(R)) on the volumetricflow rate (φ) is determined empirically at a start of the operation in anewly installed HVAC system (10), and the HVAC system (10) or morespecifically the individual components are changed or replaced, when theempirically determined dependences make it necessary.
 9. The method, asclaimed in claim 7, wherein temperature sensors (16, 17) for determiningthe temperature differential ΔT between the supply temperature (T_(V))and the return temperature (T_(R)) as well as at least one flow sensor(18) for determining the volumetric flow rate (φ) are provided in theHVAC system (10) for carrying out the operation, and wherein thetemperature and flow sensors (16, 17 and/or 18) are used for empiricallydetermining the dependence of the flow of energy (E) and/or thetemperature differential ΔT between the supply temperature (T_(V)) andthe return temperature (T_(R)) on the volumetric flow rate (φ).
 10. Anadaptive variable flow Heating, Ventilation and Air Conditioning (HVAC)system (10), comprising: a primary circuit (26), which is traversed bythe flow of an energy transporting medium, at least one energy consumer(11, 12, 13), which is connected to the primary circuit (26) by way of asupply line (14) and a return line (15), temperature sensors (16, 17)for determining the temperature differential ΔT between the supplytemperature (T_(V)) and the return temperature (T_(R)) at the energyconsumer (11, 12, 13) as well as at least one flow sensor (18) fordetermining the volumetric flow rate (φ) through the energy consumer(11, 12, 13), and a controller (21, 22) that is connected to thetemperature and flow sensors (16, 17 and/or 18), wherein the controller(21, 22) receives and stores measurement values, which are outputtedsimultaneously by the temperature and flow sensors (16, 17 and/or 18),at different times, wherein a dependence of the flow of energy (E) onthe volumetric flow rate (φ) is repeatedly determined empirically atvarying time intervals by the controller, and wherein, on the basis ofthe determined dependence, an upper limit value (E_(max)) of the flow ofenergy (E) is established, and said upper limit value is not exceededwhile the HVAC system (10) is running.
 11. The HVAC system, as claimedin claim 10, wherein the controller (21, 22) comprises a data logger(22).
 12. The HVAC system, as claimed in claim 10, wherein thecontroller (21, 22) is configured for calculating and assigning the flowof energy (E) from and/or to the measurement values outputted by thetemperature and flow sensors (16, 17 and/or 18).
 13. The HVAC system, asclaimed in claim 10, wherein the controller includes a control unit,which controls and/or regulates by way of a control valve (19) thevolumetric rate of flow (φ) through the energy consumer (11, 12, 13) andinto which the limit values (E_(max)) for the flow of energy (E) can beentered.
 14. The HVAC system, as claimed in claim 13, wherein thecontrol unit is connected to the temperature and flow sensors (16, 17and/or 18).
 15. The HVAC system, as claimed in claim 10, wherein thetemperature sensors (16, 17) comprise a first temperature sensor (16)for measuring the supply temperature and a second temperature sensor(17) for measuring the return temperature, and wherein the at least oneflow sensor comprises a flowmeter (18), which is disposed in the supplyline (14) or the return line (15) of the energy consumer (11, 12, 13).16. The HVAC system, as claimed in claim 10, wherein the energy consumer(11, 12, 13) comprises a heat exchanger (11), by means of which energyis released to a secondary loop (27).
 17. An adaptive variable flowHeating, Ventilation and Air Conditioning (HVAC) system (10),comprising: a primary circuit (26), which is traversed by the flow of anenergy transporting medium, at least one energy consumer (11, 12, 13),which is connected to the primary circuit (26) by way of a supply line(14) and a return line (15), temperature sensors (16, 17) fordetermining the temperature differential ΔT between the supplytemperature (T_(V)) and the return temperature (T_(R)) at the energyconsumer (11, 12, 13) as well as at least one flow sensor (18) fordetermining the volumetric flow rate (φ) through the energy consumer(11, 12, 13), and a controller (21, 22) that is connected to thetemperature and flow sensors (16, 17 and/or 18), wherein the controller(21, 22) receives and stores measurement values, which are outputtedsimultaneously by the temperature and flow sensors (16, 17 and/or 18),at different times, wherein dependence of the temperature differentialΔT between the supply temperature (T_(V)) and the return temperature(T_(R)) on the volumetric flow rate (φ) is repeatedly determinedempirically at varying time intervals by the controller, and wherein, onthe basis of the determined dependence, a lower limit value (ΔT_(min))of the temperature differential ΔT between the supply temperature(T_(V)) and the return temperature (T_(R)) is established.
 18. The HVACsystem, as claimed in claim 17, wherein the controller (21, 22)comprises a data logger (22).
 19. The HVAC system, as claimed in claim17, wherein the controller (21, 22) is configured for calculating andassigning the flow of energy (E) from and/or to the measurement valuesoutputted by the temperature and flow sensors (16, 17 and/or 18). 20.The HVAC system, as claimed in claim 17, wherein the controller includesa control unit, which controls and/or regulates by way of the controlvalve (19) the volumetric rate of flow (φ) through the energy consumer(11, 12, 13) and into which the limit value (ΔT_(min)) for thetemperature differential ΔT between the supply temperature (T_(V)) andthe return temperature (T_(R)) can be entered.
 21. The HVAC system, asclaimed in claim 20, wherein the control unit is connected to thetemperature and flow sensors (16, 17 and/or 18).
 22. The HVAC system, asclaimed in claim 17, wherein the temperature sensors (16, 17) comprise afirst temperature sensor (16) for measuring the supply temperature and asecond temperature sensor (17) for measuring the return temperature, andwherein the at least one flow sensor comprises a flowmeter (18), whichis disposed in the supply line (14) or the return line (15) of theenergy consumer (11, 12, 13).
 23. The HVAC system, as claimed in claim17, wherein the energy consumer (11, 12, 13) comprises a heat exchanger(11), by means of which energy is released to a secondary loop (27). 24.An adaptive variable flow Heating, Ventilation and Air Conditioning(HVAC) system (10), comprising: a primary circuit (26), which istraversed by the flow of an energy transporting medium, at least oneenergy consumer (11, 12, 13), which is connected to the primary circuit(26) by way of a supply line (14) and a return line (15), temperaturesensors (16, 17) for determining the temperature differential ΔT betweenthe supply temperature (T_(V)) and the return temperature (T_(R)) at theenergy consumer (11, 12, 13) as well as at least one flow sensor (18)for determining the volumetric flow rate (φ) through the energy consumer(11, 12, 13), and a controller (21, 22) that is connected to thetemperature and flow sensors (16, 17 and/or 18), wherein the controller(21, 22) receives and stores measurement values, which are outputtedsimultaneously by the temperature and flow sensors (16, 17 and/or 18),at different times, wherein dependence of the flow of energy (E) and/orthe temperature differential ΔT between the supply temperature (T_(V))and the return temperature (T_(R)) on the volumetric flow rate (φ) isrepeatedly determined empirically at varying time intervals by thecontroller, and wherein results that are obtained in each case arecompared with each other by the controller, in order to determine bymeans of the comparison a degradation of the system in function oreffect.
 25. The HVAC system, as claimed in claim 24, wherein thecontroller (21, 22) comprises a data logger (22).
 26. The HVAC system,as claimed in claim 24, wherein the controller (21, 22) is configuredfor calculating and assigning the flow of energy (E) from and/or to themeasurement values outputted by the temperature and flow sensors (16, 17and/or 18).
 27. The HVAC system, as claimed in claim 24, wherein thecontroller includes a control unit, which controls and/or regulates byway of a control valve (19) the volumetric rate of flow (φ) through theenergy consumer (11, 12, 13).
 28. The HVAC system, as claimed in claim27, wherein the control unit is connected to the temperature and flowsensors (16, 17 and/or 18).
 29. The HVAC system, as claimed in claim 24,wherein the temperature sensors (16, 17) comprise a first temperaturesensor (16) for measuring the supply temperature and a secondtemperature sensor (17) for measuring the return temperature, andwherein the at least one flow sensor comprises a flowmeter (18), whichis disposed in the supply line (14) or the return line (15) of theenergy consumer (11, 12, 13).
 30. The HVAC system, as claimed in claim24, wherein the energy consumer (11, 12, 13) comprises a heat exchanger(11), by means of which energy is released to the secondary loop (27).